Process for assessing the quality of processed material

ABSTRACT

Image areas that have been printed by specific printing plates or areas are coordinated with those specific plates or areas. A counter is coordinated with each specific image area and specific plate or area which prints it. If a predetermined number of faults are counted, a signal is generated and can be used to shut down the press or to advise the press operator of the existence of the recurring fault.

FIELD OF THE INVENTION

The present invention relates to processes for qualitative assessment ofprocessed material.

DESCRIPTION OF THE PRIOR ART

DE-OS 38 849 describes a process for detecting faults on rolled steelsurfaces. In the process those faults, which have a defined periodicity,are identified.

DE 41 29 196 A1 discloses a process for detecting faults in a textileweb. Here, the number of consecutive faults is added up. When afault-free product appears, the counter setting is returned to zero.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a process for thequalitative assessment of processed material.

This object is attained in accordance with the invention by theutilization of a process for the qualitative assessment of material byutilization of at least one photoelectric sensor and an evaluationdevice which acts with it. Image areas of the inspected material aredetected in association with possible fault sources. Each printing plateor forme on a printing cylinder which is provided with a plurality ofidentical printing formes that are arranged one behind the other isdetermined as the fault source.

Faults in the material to be inspected are systematically detected in anadvantageous manner by means of the processes of the present invention.Locating a fault is made easier by means of the specific detection ofoccurring faults, and their assignment to an associated fault source.Waste and down-times of the processing machine are reduced.

In this way, a clear association of faults to the fault- generatingprinting forme is possible, in particular in connection with rotaryprinting presses (see EP 0 406 157 B1) having a printing cylinder with aplurality of identical printing formes.

A dependable fault assessment is achieved by counting up and down inaccordance with the number of successive faulty and fault-free imageareas.

In connection with faults because of insufficient wiping of the inkedprinting formes of a steel engraving printing press in particular, itoften occurs that only one fault-free sheet follows several faultysheets, and then is again followed by several faulty sheets. If, in thiscase, the number of faulty sheets has almost reached an upper thresholdvalue, the counter setting is only reduced by one as a result of thissingle fault-free sheet, and the counter setting is increased again bythe following faulty sheets. Therefore the threshold value of thecounter setting is rapidly reached and a warning signal is triggered.Unnecessary waste is reduced by this.

BRIEF DESCRIPTION OF THE DRAWINGS

The process in accordance with the invention will be described ingreater detail in what follows and as depicted schematically in theaccompanying drawings in which:

FIG. 1 is a schematic side elevation view of a printing press and sheetinspection device in accordance with the present invention;

FIG. 2 is a top plan view of a printed sheet having image areas; and

FIG. 3 is a flow chart of the process of assessing the quality ofprocessed material in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A processing machine, for example a rotary printing press, generally at10, as seen in FIG. 1, is provided with a device 12 for the qualitativeassessment of processed material. This processed material can be printedsheet 14 or webs, for example. In the present embodiment sheets of paper14 are printed by means of the steel engraving process and arethereafter qualitatively assessed in-line.

The rotary printing press 10 can be a steel engraving printing press,for example known from EP 0 406 157 B1.

A process for assessing these sheets is known from DE 42 06 366 A1, forexample.

In accordance with the process for assessing the quality of processedmaterial in accordance with the present invention, image elements 16 ofa sheet 14 to be inspected, as seen in FIG. 2, are compared with storedimage elements of so-called “master” sheets. If one or several measuredvalues are outside of a predetermined tolerance of the correspondingmeasured values of the “master” sheet, a fault is detected. This faultcan now be signaled visually or acoustically by means of a first warningsignal. It is also possible to mark or remove the respective sheet 14containing a fault. A signal regarding the faulty sheet is supplied to acounter 18, by means of which the counter setting of a counting unit isincreased by one, for example. Now if one or several faulty sheets 14directly follow the first faulty sheet, the counter setting of thecounter 18 is increased by one for each faulty sheet, as depicted inFIG. 3. Only with faults occurring directly one after the other does thecounter 18 increase the counter setting by respectively one countingunit, for example raising it by one.

If a fault-free sheet 14 is detected following a faulty sheet, a signalfor the fault-free sheet is supplied to the counter 18, by means ofwhich the counter setting is reduced in steps by a counting unit, forexample one. If now further fault-free sheets 14 follow directly oneafter the other, the counter setting is respectively reduced by one foreach fault-free sheet. If the counter has reached a lower thresholdvalue, for example the value zero, no further downward counting isperformed.

Thus, the counter setting is changed in steps corresponding to thenumber of inspected faulty and fault-free sheets. This procedure isfollowed within a range of the counter setting from a lower thresholdvalue, for example zero, up to a selectable upper threshold value of thecounter setting, which can be set. If this threshold value has beenreached, a second warning signal is triggered and is supplied to thepress control 20, for example. This signal can cause the reduction ofthe speed of the rotary printing press 10 for example, or the stoppingof the rotary printing press 10.

This process can be applied to the total number of sheets to beinspected.

The sheets to be inspected are often processed in machines in whichcyclical faults can occur. For example, this is the case when the sheetsare printed by a rotary printing press such as the type of pressdisclosed in EP 0 406 157 B1.

This rotary printing press 10 has a plate cylinder 22, which is providedwith three printing plates 24, each of which has an identical printingforme. After inking, the non-printing areas of these printing formes arecleaned of printing ink by a common wiping device. This wiping deviceconsists, inter alia, of a wiping cylinder 26 applied under pressureagainst the printing formes 24. Now, if for example one of the threeprinting plates 24 is damaged, or part of it lies slightly lower, thewiping device 26 does not completely clean this area. Therefore eachthird sheet 14 in the stream of all of the sheets 14 produced would havea fault in the nature of a scumming area.

Scumming areas, however, can also sometimes occur over only a limitedperiod of time, for example because of slugs, which slugs are eventuallyremoved from the printing plate by the wiping device.

In this example, each printing plate 24 is assigned its own counter 12.This counter is synchronized with the rotational speed of the printingpress and with the inspection device. A signal of a fault-free, orrespectively of a faulty sheet being printed by means of a definedprinting plate is supplied only to the counter assigned to this printingplate.

Thus, only signals from the sheets printed by means of the associatedprinting plate 24 and inspected are supplied to each counter 18 assignedto this printing plate 24.

This respective counter 18 can be operated in accordance with thefollowing principle:

If a faulty sheet is detected, a signal is supplied to the respectivecounter 18, as depicted in FIG. 3, by means of which the counter settingis increased by a counting unit, for example one. This takes place inconnection with successive sheets up to a predeterminable thresholdvalue. When a fault-free sheet is detected, the counter setting isreturned to zero, and counting up of the counter setting restarts onlywhen a faulty sheet again appears. When this threshold value has beenreached, a second warning signal is issued, which is passed on, forexample, to the printer control 20 for triggering further actions.

The process described at the outset is used in a particularlyadvantageous manner for the counting operation of these cyclicallyoccurring faults. In accordance with this, the step-by-step counting upand down of the counter setting takes place as a function of therespective number of faulty and fault-free sheets.

This counting of cyclic faults is not only limited to the describedexample of plate cylinders with several printing plates, wherein thecyclical faults of successive sheets or repeats of the web are detected.Other cases of use are also possible. In this case at least oneindividual counter is assigned to each relevant one of several possiblefault sources which generate a cyclical fault.

For example, it is also possible to determine partial areas 16, i.e.windows, within a sheet, to which an individual counter is assigned.

It is of course also possible to perform the count by means of othercounting units or step sizes i.e. a step size not one, and with otherthreshold values.

While a preferred embodiment of a process for assessing the quality ofprocessed material in accordance with the present invention has been setforth fully and completely hereinabove, it will be apparent to one ofskill in the art that a number of changes in, for example, the specifictype of printing press used, the type of paper being printed on and thelike could be made without departing from the true spirit and scope ofthe present invention which is accordingly to be limited only thefollowing claims.

What is claimed is:
 1. A process for the qualitative assessment ofmaterial including: providing at least one photoelectric sensor and anevaluation device acting with it; providing a rotary printing presshaving a printing cylinder; providing several printing forms on saidprinting cylinder; identifying each of said several printing forms onsaid printing cylinder as a separate fault source; forming a pluralityof printed image areas on the material using said several printingforms; assigning each one of said plurality of printed image areasformed on the material to its associated one of said several printingforms; detecting faulty and fault-free ones of said plurality of printedimage areas formed on the material using said at least one photoelectricsensor and said evaluation device acting with it; associating eachfaulty one of said plurality of printed image areas formed on thematerial with an associated one of said separate fault sources;providing a separate counter for each one of said separate faultsources; increasing a counter setting of each said separate counter upondetecting a faulty one of said printed image areas formed by saidassociated one of said separate fault sources; and decreasing saidcounter setting of each said separate counter upon detecting afault-free one of said printed image areas formed by said associated oneof said separate fault sources.
 2. A process for the qualitativeassessment of printed material including: providing at least onephotoelectric sensor and an evaluation device acting with it; providinga plurality of pieces of printed material; providing an image area oneach of the plurality of pieces of printed material to be assessed.providing a counter having a changeable counter setting; assigning saidcounter to said image area; detecting faulty and fault-free ones of saidimage area utilizing said at least one photoelectric sensor and saidevaluation unit associated with it; increasing said counter setting byone counting unit when one of said plurality of image areas is faulty;decreasing said counter setting by one counting unit when one of saidplurality of image areas is fault-free; providing an upper thresholdvalue for said counter setting; activating a signal when said countersetting reaches said upper threshold value; providing a lower thresholdvalue for said counter setting; and decreasing said counter setting onlyas low as said lower threshold value.
 3. The method of claim 2 furtherincluding increasing said counter setting by one counting unit when saidimage area is faulty and decreasing said counter setting by one countingunit when said image area is fault-free.
 4. The process of claim 1further including utilizing said printing cylinder to print entiresheets and designating each of said sheets as said image area.
 5. Theprocess of claim 1 further including utilizing said printing cylinder toprint a repeat on a web and designating each such repeat as an imagearea.
 6. The process of claim 2 further including selecting said imagearea as an entire sheet of printed material.
 7. The process of claim 2further including selecting said image area as a repeat on a web ofprinted material.